If you've ever tried copying and pasting a multi-line address into Google Maps just to realize that an input box will only take one line at a time—meaning that you have to copy and paste each line individually—there's a simple Firefox tweak that will solve this problem:

Type "about:config" in the location bar. In the "Filter" field type "singleline." You can set the value to 2 for editor.singleLine.pasteNewlines, which will allow pasting of multiple lines to input boxes.

Of course, this tweak works for any input box, so if you've bumped up against the multi-line paste problem elsewhere, consider it a problem of the past. Thanks Nikolai!